A major aim of our work is the definition, in precise molecular terms, of the function of E. coli DNA ligase, E. coli DNA polymerase I, T4 DNA ligase and T4 DNA0polymerase in DNA replication. A second aim is the identification and characterization of as yet unknown enzymes and factors involved in DNA replication. Our specific goals for the coming year are the following: a. Initation of an x-ray crystallographic analysis of E. coli DNA ligase in order to obtain a detailed picture of its three dimensional structure. b. Continuation of our efforts to purify the alpha DNA polymerase of Drosophila melanogaster embryos to homogeneity and to stabilize the pure protein. An immediate aim is to accumulate 1 to 2mg of pure enzyme for the detailed analysis of its structure and mechanism.